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Avalanche Forecast

Archived

Mar 30th, 2017–Mar 31st, 2017

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Columbia.

Warming and solar induced avalanches are likely. Smaller wind slabs, storm slabs or cornice fall could "step down" and release persistent weak layers resulting in large avalanches.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Drier, sunny conditions expected on Friday and then back to unsettled weather for the weekend.Friday: A mix of sun and cloud. Alpine temperatures near -2 and freezing levels 1900 m. Ridgetop winds light from the South.Saturday: Snow amounts 5-10 cm. Alpine temperatures near -23and freezing levels 1500 m. Ridgetop winds moderate -strong from the West.Sunday: Mix of sun and cloud. Alpine temperatures near -5 and freezing levels 1400 m. Ridgetop winds light with strong gusts from the West.

Avalanche Summary

On Wednesday, storm slabs proved to be reactive and ran naturally up to size 2.5 with a couple larger size 3 and 3.5. Storm slabs were also reportedly reactive to skier triggers up to size 1.5 at treeline elevations. On Friday natural avalanche activity will remain likely with the strong influence of solar radiation,  warming and wind. Fragile cornices are also suspect which are a large enough to trigger deeper slabs to release on the slopes below. If you're traveling below treeline where the avalanche hazard may be lower than it is in the alpine you still need to be diligent with your terrain use and focus on potential overhead hazards by avoiding lingering in run-out zones where large avalanches to come from above. Check out the recent Forecaster Blogs for more details.

Snowpack Summary

30-50 cm of recent storm snow has accumulated at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 80-120 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a concern during this stormy period ending with warmer temperatures and sunshine. The snowpack does not adjust well to change, and these deeper weak layers should remain on your radar through the forecast period.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.